Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$227.96	6.769%	$243.3906	$243.39	$243.40	$243.40
Purchase #2	$25.31	9.431%	$27.697	$27.70	$27.70	$27.70
Purchase #3	$55.79	9.595%	$61.1431	$61.14	$61.15	$61.10
Purchase #4	$40.63	5.460%	$42.8484	$42.85	$42.85	$42.80
Purchase #5	$239.78	13.169%	$271.3566	$271.36	$271.35	$271.40
Purchase #6	$240.41	13.461%	$272.7716	$272.77	$272.75	$272.80
Purchase #7	$88.82	13.125%	$100.4776	$100.48	$100.50	$100.50
7 purchase totals =	$918.70		$1,019.6849	$1,019.69	$1,019.70	$1,019.70